There have hitherto been proposed oxygen detecting agents using organic dyes which undergo reversible color change due to oxidation and reduction. Commercially available oxygen detecting agents (for example, trade name “Ageless Eye,” manufactured by Mitsubishi Gas Chemical Company, Inc.) are function products simply showing by color change that the oxygen concentration in a transparent packaging container is in a deoxygenated state of less than 0.1% by volume, and are used together with oxygen scavengers for food freshness maintenance, quality maintenance of medical pharmaceuticals and the like. Many of conventional oxygen detecting agents allow the presence or absence of oxygen in a system to be visually identifiable by using a redox dye in combination with an appropriate reducing agent.
In conventional oxygen detecting agents, organic dyes typified by methylene blue are used as redox dyes, and these organic dyes sometimes cause transfer to and contamination of, for example, packaging materials. In this regard, for example, Patent Literature 1 proposes an oxygen indicator in which an oxygen detecting agent composition containing methylene blue and a cyclic olefin copolymer are laminated on each other. Patent Literature 2 proposes an oxygen detecting agent composition in which methylene blue is impregnated into a layered silicate.